CBS and chronic myelogenous leukemia, BCR-ABL1 positive: In mammals, hydrogen sulfide (H2S) is mainly produced by three enzymes including cystathionine β-synthase (CBS), cystathionine γ-synthase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST).27 To examine the expressions of these three enzymes and H2S in bone marrow of the newly diagnosed CML pediatric patients (Table 1) and CML-derived cell line K562, RT-PCR, Western blot, and methylene blue method were performed.